AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Composition and Photochemistry of Biodiesel and Diesel Fuel SOA
SANDRA BLAIR, Amanda MacMillan, Greg Drozd, Allen H. Goldstein, Peng Lin, Julia Laskin, Alexander Laskin, Sergey Nizkorodov, University of California, Irvine
Abstract Number: 72 Working Group: Aerosol Chemistry
Abstract The physical and chemical properties of “fresh” versus “aged” secondary organic aerosol (SOA) strongly depend on the type of aging. This study focuses on SOA aging arising from the condensed-phase photolysis of laboratory-generated particulate organic compounds in photooxidized biodiesel (BDSL) and diesel (DSL) fuel SOA. The presence of NOx, SO$_2, NH$_3, and relative humidity (RH) may change the composition and absorption properties of this SOA and, furthermore, may have an effect on its photochemistry. SOA composition before and after direct photolysis of particulate organic compounds was measured using several analytical techniques including: aerosol mass spectrometry (AMS), high-resolution nanospray desorption electrospray ionization mass spectrometry (nano-DESI), and 2D gas chromatography mass spectrometry. This paper will discuss the effect of SO$_2, NH$_3, RH, and UV photolysis on (1) particle mass concentration, (2) chemical composition, and (3) mass absorption coefficient (MAC) of BDSL, DSL, and BDSL/DSL SOA. Preliminary results show that addition of SO$_2 produces organosulfates in the condensed-phase. The mass absorption coefficients show different trends between the BDSL and DSL samples, but a much smaller change was observed for SOA generated from a BDSL/DSL mixture. There was a larger photolytic loss of organic material relative to inorganic sulfate and mass absorption coefficients decreased upon irradiation. After photolysis, little change was observed in average composition, but significant change was observed in molecular composition.